Why does my Dark Chocolate Peanut Butter Cup say "contains milk" when there are no milk products in the ingredients?

Why does my Dark Chocolate Peanut Butter Cup say "contains milk" when there are no milk products in the ingredients?

Even though there are no milk ingredients added in our delicious Dark Chocolate Peanut Butter Cups and the recipe has not changed, we did update our labels a few years ago. Our new labels now indicate “contains trace amounts of milk” because they are processed on shared equipment with our Milk Chocolate and White Chocolate Peanut Butter Cups, which do contain dairy. While there is a sanitation process between each batch, the reason we made this change is two-fold, both deriving from our company’s primary fundamental – safety.
Justin’s is very careful about choosing and selecting only the highest quality chocolatiers to source not only our dark chocolate but all of the chocolate used in our products. However, it is common practice for the chocolate industry to process cocoa beans on shared equipment with milk containing ingredients. So, while we are extremely careful, the chance of cross-contact exists even before we purchase the chocolate.
In addition to sourcing the highest-quality chocolate, we use the best manufacturing practices for safety and quality. Because our Dark Chocolate Peanut Butter Cups share equipment with our Milk Chocolate and White Chocolate Peanut Butter Cups, which do contain dairy, the opportunity for cross contact as we manufacture the peanut butter cups at our facilities also exists. We felt this precautionary message may help our friends who are extremely sensitive to dairy .